1. Field of the Invention
The present invention relates to a substrate for an ink jet head (hereinafter, also simply called as “substrate”) provided with energy generating members generating energy used for discharging an ink, and an ink jet head including the substrate.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. S59-095154 discloses an ink jet recording apparatus of a method of vertically discharging an ink to a substrate from an ink supply port.
A substrate loaded on an ink jet recording apparatus of this kind has an ink supply port forming a rectangular opening so as to penetrate through a center of the substrate. The substrate supplies an ink or multicolor inks with high density to a discharge port from an ink supply port. A heat generating resistance element is arranged along the long side of the ink supply port, and is connected with an electrode pad with wirings to receive supply of a current from the electrode pad.
The electrode pad is provided perpendicularly to the side of a substrate outer periphery which is horizontal with the short side of the ink supply port, and at this position, the electrode pad is connected with an external wiring board. When the electrode pad is provided along the side of the outer periphery of the substrate to be parallel with the short side of the ink supply port, the length of electrode wiring until the electrode wiring reaches heat generating resistance elements from the electrode pad becomes long. The length of the electrode wiring and the resistance of the electrode wiring are proportional to each other. Therefore, when the length of the electrode wiring becomes long, the resistance of the electrode wiring becomes large. In this case, if a plurality of heat generating resistance elements connected to the same electrode wiring is driven at the same time, the voltage drop difference in the wiring portions significantly differs depending on the number of the heat generating resistance elements which are driven at the same time. Thus, it becomes difficult to obtain proper foaming, and high-quality recording becomes difficult.
Here, the ink jet recording head described in Japanese Patent Application Laid-Open No. H10-044416 deals a plurality of heat generating resistance elements disposed on the substrate as one block, and has a plurality of blocks. Only one heat generating resistance element out of each of the blocks is driven at the same time. This is called block time-sharing drive. According to this, the difference in voltage drop in the wiring portions connected to the heat generating resistance elements can be made constant, and therefore, proper foaming can be obtained.
However, there is the problem that when the width of the electrode wiring on the substrate becomes large, the size of the substrate also increases.
Japanese Patent Application Laid-Open No. S62-13367 discloses a thermal head which can suppress unevenness of density by making the heat generation temperatures of respective heat generating resistance elements substantially constant. An individual electrode is connected to one end of a heat generating resistance element. A common electrode is connected to the other end of the heat generating resistance element. The respective heat generating resistance elements are arranged to be parallel at predetermined intervals. These heat generating resistance elements are divided into eight blocks, and an L-shaped slit for restricting the flow of a current is provided between the blocks. A resistance member for fine-adjusting a voltage is disposed in each of current passages of the common electrode divided by the L-shaped slits (FIGS. 4A and 4B in Japanese Patent Application Laid-Open No. S62-013367).
However, in this case, in order to place the resistance members at the positions illustrated in FIGS. 4A and 4B, the width of the electrode wiring on the substrate also needs to be larger than a certain extent, and there is the problem of increasing the size of the substrate.